This invention relates to the esterification of carboxyaromatics, particularly through the reaction of an anhydride of a carboxyaromatic with a fluorinated alcohol followed by reaction of the resulting ester/acid with an epoxide. Such an esterification process is generally known, especially in the preparation of compounds capable of imparting oil and/or water repellency to textiles such as polyester and nylon fibers.
In particular, U.S. Pat. No. 4,209,610 and G.B. Pat. No. 1,543,081 disclose compounds useful for imparting oil and water repellency which are prepared by contacting in solution an anhydride of a carboxybenzene and various fluorinated alcohols to form the corresponding fluorinated ester/acid, and then contacting said ester/acid in solution with an epoxide. More particularly, in Example VIII of U.S. Pat. No. 4,209,610, pyromellitic dianhydride (PMDA) is esterified in DMF with a mixture of perfluoroalkyl-ethanols to form the corresponding diester/diacid, which is then further reacted (in DMF) with excess epichlorohydrin, using a little triethylamine as catalyst, to esterify the remaining carboxyl groups to form the tetraester, which is precipitated out with ice water.
Similarly, in European Patent application No. 19,732, published Dec. 10, 1980, esterification of carboxybenzenes in N-methylpyrrolidone (NMP) solvent is disclosed and shown to be superior in comparative testing to a like product made in DMF.
In U.S. Pat. No. 4,252,982, such esterifications of carboxybenzenes are shown in aliphatic ester solvents such as butyl acetate. The use of the aliphatic ester solvents is said to overcome the waste water problem which results when DMF or NMP is employed as the solvent for such esterifications. When DMF or NMP is employed, the final product must be precipitated out with water, which takes up the solvent and thus requires waste water treatment. The advantage in using the aliphatic ester solvent is that it can be distilled from the desired product. However, the use of the aliphatic ester solvent results in a slower reaction rate, presents a flammability hazard, and produces a slightly inferior product in comparison with the NMP process.